AWS LambdaとSlack incoming webhookでサイトの生存確認チェッカーを作る

from __future__ import print_function

import datetime
import urllib.request
import json


SITES = [
    'https://www.example.com/',
    'https://ここにチェックしたいサイトを入れてね'
    ]
DESCRIPTION = "サイトの生存確認用チェッカーからの連絡"
SLACK_WEBHOOK = 'ここにSlackのincoming webhookのURLをコピペ'
DIFF_JST_FROM_UTC = 9

def lambda_handler(event, context):
    for site in SITES:
        request = urllib.request.Request(site)
        now = datetime.datetime.now() + datetime.timedelta(hours=DIFF_JST_FROM_UTC)
        nowstr = now.strftime("%Y/%m/%d %H:%M:%S")
        try:
            with urllib.request.urlopen(request) as res:
                url = res.geturl()
                print(url)
                if not url == site :
                    raise ValueError("error!")
        except urllib.error.HTTPError as e:
            print('Check failed!')
            post_slack("<!here>\n{0}\n{1}\n※※※※※※※※\n{2}\nHTTP通信エラー\n※※※※※※※※".format(nowstr,site,DESCRIPTION))
            raise
        except urllib.error.URLError as e:
            print('Check failed!')
            post_slack("<!here>\n{0}\n{1}\n※※※※※※※※\n{2}\n URLエラー\n※※※※※※※※".format(nowstr,DESCRIPTION))
            raise
        except ValueError as e:
            print('Check failed!')
            post_slack("<!here>\n{0}\n※※※※※※※※\n{1}\n ルーティングエラー：リダイレクトされている\n※※※※※※※※".format(nowstr,DESCRIPTION))
            raise
        else:
            print('Check passed!')
            # post_slack("{0}\n{1} 成功".format(nowstr,DESCRIPTION))
            return
        finally:
            print('Check complete at {}'.format(str(datetime.datetime.now())))

def post_slack(message):

    send_data = {
        "username": "AWS Lambda",
        "text": message,
    }
    send_text = "payload=" + json.dumps(send_data)
    request = urllib.request.Request(
        SLACK_WEBHOOK, 
        data=send_text.encode("utf-8"), 
        method="POST"
    )
    with urllib.request.urlopen(request) as response:
        response_body = response.read().decode("utf-8")